The present invention relates to medical devices in general, and in particular to atherectomy devices for removing deposits from a vessel.
Atherectomy burrs are becoming commonly used medical devices that remove deposits from a patient""s vessel. A typical atherectomy device includes a driveshaft that is rotated by a gas turbine or electric motor and has an atherectomy burr disposed at its distal end. The atherectomy burr is typically an ellipsoidally shaped metal bead having an abrasive outer coating. The coating, which usually comprises a diamond grit, removes deposits from a vessel when the burr is rotated at high speed and advanced into the deposits or an occlusion.
While the use of an atherectomy device provides a minimally invasive technique for removing deposits from a vessel, there are some situations where the use of such devices has been avoided. For example, in saphenous vein grafts (SVGs), deposits tend to be loosely calcified and friable and can break up into large pieces before a high-speed atherectomy burr can disintegrate them. These lesions are also often covered with a fibrous cap, which is tough and flexible enough to resist disintegration by a high speed cutting burr. Therefore, these types of lesions often require ablation with a less differentially cutting low speed cutter. However, the anastomosis, or entry point, into the vein graft is often highly angulated and surrounded by scar tissue which is more suitable for removal with a more differentially cutting high speed cutting burr. Therefore, in order to perform an atherectomy procedure in an SVG, multiple cutting burrs must be employed, thereby adding to the expense and time required to perform the procedure.
In order to increase the number of locations in the body where a less invasive atherectomy procedure can be used to remove deposits from a vessel without the need to use multiple burrs, there is a need for an atherectomy device that can easily remove harder, more dense material in addition to softer, more friable occluding material such as that typically found in an SVG.
To address the above-mentioned shortcomings, the present invention is a bi-directional atherectomy device that includes a source of rotational motion and a driveshaft coupled to the source of rotational motion. An atherectomy burr at the distal end of the driveshaft has a number of cutting blades having a less aggressive cutting action when rotated in a first direction and a more aggressive cutting action when rotated in a second direction.
In one embodiment of the invention, the number of cutting blades have an abrasive surface that is substantially parallel to the outer surface of the burr and a cutting surface that is substantially perpendicular to the outer surface of the burr. When rotated in the first direction, the less aggressive, abrasive surface removes deposits from a vessel. When rotated in the second direction, the more aggressive, cutting surface removes deposits from the vessel.
In one embodiment of the invention, the one or more blades are parallel to the longitudinal axis of the burr. In another embodiment of the invention, the one or more cutting blades are spiraled along the length of the burr body.